chapter31_Sections 1

Report
Cecie Starr
Christine Evers
Lisa Starr
www.cengage.com/biology/starr
Chapter 31
Endocrine Control
(Sections 31.1 - 31.5)
Albia Dugger • Miami Dade College
31.1 Hormones in the Balance
• Some synthetic chemicals, such as DDT (pesticide), PCBs
(used in electronic products, caulking, and solvents), and
Atrazine (herbicide) are endocrine disrupters that harm the
environment and threaten human health
• endocrine disrupter
• Synthetic chemical that adversely affects hormone
production or function
Costs of Herbicide Applications
• Atrazine keep cornfields nearly weed-free – it also interferes
with sexual development in amphibians
31.2 Vertebrate Endocrine System
• Animal cells communicate with adjacent cells by way of gap
junctions, neurotransmitters, and local signaling molecules
• Animal hormones travel through the blood and can carry
signals between cells in distant parts of the body
• All hormone-secreting glands and cells in a body constitute
the animal’s endocrine system
Mechanisms of
Intercellular Signaling
• Signaling molecules exert effects only when they bind to a
matching receptor on or inside a “target” cell
• Local signaling molecules diffuse a short distance through
interstitial fluid and bind to nearby cells
• Example: Prostaglandins released by injured cells activate
pain receptors and increase local blood flow
• Animal hormones circulate through the bloodstream, and
exert their effects on a greater number of cells
Key Terms
• local signaling molecule
• Chemical signal, such as a prostaglandin, that is secreted
by one cell and affects neighboring cells in an animal body
• animal hormone
• Intercellular signaling molecule secreted by an endocrine
gland or cell
Discovery of Hormones
• Physiologist E. Starling coined the term “hormone” to describe
his discovery of secretin (the hormone that stimulates the
pancreas to secrete bicarbonate)
• Endocrine glands and other structures that secrete hormones
are collectively referred to as an animal’s endocrine system
• endocrine system
• Hormone-producing glands and secretory cells of a
vertebrate body
The Endocrine System
The Endocrine System
Hypothalamus
Makes and secretes releasers and
inhibitors, hormones that act in the
anterior lobe of the pituitary. Also makes
antidiuretic hormone and oxytocin,
which are stored in and released from the
posterior lobe of the pituitary.
Pituitary gland
Anterior lobe makes and secretes
ACTH, TSH, LH, FSH (stimulate secretion
by other endocrine glands), prolactin
(acts on mammary glands) and growth
hormone (affects overall growth).
Posterior lobe secretes antidiuretic
hormone (acts on kidneys) and oxytocin
(acts on uterus and mammary glands).
Both are made in the hypothalamus.
Adrenal glands (one pair)
Adrenal cortex makes and secretes
cortisol (affects metabolism, immune
response), aldosterone (acts in kidneys),
small amount of sex hormones. Adrenal
medulla makes and secretes
norepinephrine and epinephrine, which
prepare body for exciting or dangerous
situations.
Ovaries (one pair of female gonads)
Make and secrete progesterone and
estrogens (affect primary sex organs and
influence secondary sexual traits).
closer view of the
hypothalamus and
pituitary gland
hypothalamus
pituitary gland
Pineal gland
Makes and secretes melatonin (affects
sleep/wake cycles, onset of puberty).
Thyroid gland
Makes and secretes thyroid hormone
(metabolic and developmental effects)
and calcitonin (lowers blood calcium).
Parathyroid glands (four)
Make and secrete parathyroid hormone
(raises blood calcium level).
Thymus gland
Makes and secretes thymosins (act in
maturation of T cells, a type of white
blood cell).
Pancreas
Makes and secretes insulin (lowers
blood glucose level) and glucagon
(raises blood glucose level).
Testes (one pair of male gonads)
Make and secrete testosterone and other
androgens (affect primary sex organs
and influence secondary sexual traits).
Fig. 31.2, p. 505
ANIMATION: Major human endocrine
glands
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Neuroendocrine Interactions
• The endocrine system and nervous system are closely linked
• Hormones affect nervous processes such as sleep/wake
cycles, emotion, mood, and memory
• The nervous system affects hormone secretion
• Both respond to signals from the hypothalamus, and both
affect the activity of the same organs
Key Concepts
• The Vertebrate Endocrine System
• Hormones and other signaling molecules regulate the
pathways that control metabolism, growth, development,
and reproduction
• Nearly all vertebrates have an endocrine system
composed of the same hormone-producing structures
31.3 The Nature of Hormone Action
• For a hormone to have an effect, it must bind to receptors on
or inside a target cell
• Hormones initiate responses in different ways, but in all
cases, binding to a receptor is reversible and the response
declines over time
Reception, Transduction, Response
• Signal processing is a three-step process:
Signal Reception
Signal Transduction
Cellular Response
• A chemical signal binds to a receptor on a target cell, the
signal is transduced (converted to a form that acts in the
receiving cell), and the target cell makes a response
Types of Hormones
• Animal hormones are chemical signals derived from either
cholesterol or amino acids
• Steroid hormones are lipid soluble and derived from
cholesterol; they enter cells and bind to receptors inside them
• steroid hormone
• Hormone such as testosterone that is derived from
cholesterol
Types of Hormones (cont.)
• Peptide and protein hormones are derived from amino acids
• They bind to receptors in the cell membrane
• Binding often triggers formation of a second messenger, a
molecule that elicits changes inside the cell
Categories of Hormones
Intracellular Receptors
• Steroid hormones form a hormone-receptor complex by
binding to a receptor in the cytoplasm or nucleus
• The hormone-receptor complex binds to a promoter near a
hormonally regulated gene
• Transcription and translation result in a protein product, such
as an enzyme, that carries out the target cell’s response to
the signal
Steroid Hormone Action
Steroid
Hormone
Action
1 A steroid hormone
molecule is moved from
blood into interstitial fluid
bathing a target cell.
2 Being lipid
soluble, the
hormone
easily
diffuses
across the
cell’s plasma
membrane.
3 The hormone
diffuses through the
cytoplasm and nuclear
envelope. It binds with
its receptor in the
nucleus.
5 The
resulting
mRNA moves
into the
cytoplasm and
is transcribed
into a protein.
A Example of steroid
hormone action inside
a target cell.
gene product
receptor
hormone–
receptor
complex
4 The
hormone–
receptor
complex
triggers
transcription of a
specific
gene.
Fig. 31.3a, p. 507
ANIMATION: Hormones and target cell
receptors
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Receptors at the Plasma Membrane
• Peptide and protein hormones bind to receptor proteins in a
target cell’s plasma membrane
• Binding causes a second messenger to form, which causes
more cellular changes
• second messenger
• Molecule that forms inside a cell when a hormone binds at
the cell surface
• Sets in motion reactions that alter activity inside the cell
Peptide Hormone Action
Peptide
Hormone
Action
A peptide hormone
1 molecule,
glucagon,
diffuses from blood into
interstitial fluid bathing
the plasma membrane
of a liver cell.
unoccupied glucagon
receptor at target cell’s
plasma membrane
ATP
cyclic
AMP
+ Pi
2 Glucagon binds
with a receptor.
3 Cyclic AMP
Binding activates an
activates another
enzyme that catalyzes enzyme in the cell.
the formation of
cyclic AMP from ATP
inside the cell.
4 The enzyme activated by
B Example of peptide
hormone action
inside a target cell.
cyclic AMP activates another
enzyme, which in turn
activates another kind that
catalyzes the breakdown of
glycogen to its glucose
monomers.
5
The enzyme
activated by
cyclic AMP
also inhibits
glycogen
synthesis.
Fig. 31.3b, p. 507
Steroid Hormone Receptors
• Some cells have receptors for steroid hormones at the
plasma membrane
• Binding a steroid hormone triggers a fast response by way of
a second messenger, or by altering a property of the
membrane
• Example: When aldosterone binds to target cells in kidneys,
target cells quickly become more permeable to sodium ions
Receptor Function and Diversity
• Hormone receptors are proteins
• Mutations can result in receptors with a lowered capacity for
binding hormone, or none at all
• Variations in receptor structure also affect responses to
hormones; different tissues often have receptor proteins that
respond in different ways to binding of the same hormone
Example: ADH Receptor Diversity
• ADH (antidiuretic hormone) binds to kidney cells and helps
maintain solute concentrations in the internal environment
• ADH also binds to receptors in blood vessels and helps
maintain blood pressure by causing vessels to narrow
• ADH also binds to brain cells and influences sexual and social
behavior
Key Concepts
• Signaling Mechanisms
• A hormone travels through the blood and acts on any cell
that has receptors for it
• Receptor activation leads to transduction of the signal and
a response in the targeted cell
• Hormones are derived from either cholesterol or amino
acids
31.4 The Hypothalamus
and Pituitary Gland
• The hypothalamus and pituitary gland deep inside the brain
control the activities of many other endocrine glands
• hypothalamus
• Forebrain region that controls processes related to
homeostasis and has endocrine functions
• pituitary gland
• Pea-sized endocrine gland in the forebrain that interacts
closely with the adjacent hypothalamus
Hypothalamus and Pituitary Gland
• The hypothalamus connects structurally and functionally with
the two lobes of the pituitary gland
Hypothalamus and Pituitary Gland
hypothalamus
anterior
lobe of
pituitary
posterior
lobe of
pituitary
p. 508
Functions of the Hypothalamus
• The hypothalamus is the main center for control of the internal
environment
• Axons of neurons in the hypothalamus extend into the
posterior pituitary, where they release oxytocin and
antidiuretic hormone
• Releasing hormones and inhibiting hormones secreted by
the hypothalamus control the secretion of hormones made by
the anterior lobe of the pituitary
Key Terms
• releasing hormone
• Hormone that is secreted by one endocrine gland and
stimulates secretion by another
• inhibiting hormone
• Hormone that is secreted by one endocrine gland and
discourages secretion by another
Posterior Pituitary Hormones
• The posterior pituitary secretes hormones synthesized in the
hypothalamus:
• Oxytocin targets smooth muscle in mammary glands
during nursing and the uterus during birth
• Antidiuretic hormone concentrates the urine by increasing
reabsorption of water in kidney tubules
Posterior Pituitary Function
1. Cell bodies of secretory neurons in hypothalamus synthesize
ADH or oxytocin
2. ADH or oxytocin moves downward inside axons of secretory
neurons and accumulates in the axon terminals
3. Action potentials trigger release of hormones, which enter
blood capillaries in the posterior lobe of the pituitary
4. Blood vessels carry hormones to the general circulation
Posterior Pituitary Function
Posterior Pituitary Function
Cell bodies of
secretory neurons
in hypothalamus
synthesize ADH or
oxytocin.
1
The ADH or
oxytocin moves
downward inside the
axons of the secretory
neurons and
accumulates in the
axon terminals.
2
Action potentials
trigger the release of
these hormones,
which enter blood
capillaries in the
posterior lobe of the
pituitary.
3
Blood
vessels carry
hormones to
the general
circulation.
4
Fig. 31.4, p. 509
Anterior Pituitary Hormones
• The anterior pituitary makes hormones and secretes them in
response to hormones from the hypothalamus
• Four anterior pituitary hormones (ACTH, TSH, FSH, LH)
hormones target other glands
• Prolactin encourages milk production
• Growth hormone (GH) secreted by the anterior pituitary acts
throughout the body
Growth Hormone Disorders
• Pituitary gigantism and dwarfism result from mutations that
affect GH secretion or GH receptors
• Over-secretion of growth hormone in children leads to
pituitary gigantism
• Low GH secretion in childhood causes pituitary dwarfism
Pituitary Gigantism
• One of the world’s
tallest men, Bao Xishun
stands 2.36 meters (7
feet 9 inches) tall
Anterior Pituitary Function
1. Neurons in the hypothalamus secrete inhibitors or releasers
into the stalk that connects to the pituitary
2. Blood carries inhibitors or releasers to the anterior pituitary
3. Inhibitors or releasers diffuse out of capillaries in the anterior
pituitary and bind to target cells
4. Encouraged by a releaser, anterior pituitary cells secrete a
hormone that enters the general blood circulation
Anterior Pituitary Function
Anterior Pituitary Function
Cell bodies of secretory
neurons in hypothalamus
synthesize inhibitors or
releasers that are secreted
into the stalk that connects
to the pituitary.
1
The inhibitors or
releasers picked up by
capillaries in the stalk
get carried in blood to
the anterior pituitary.
2
When encouraged
by a releaser,
anterior pituitary
cells secrete
hormone that enters
blood vessels that
lead into the general
circulation.
4
The inhibitors or
releasers diffuse
out of capillaries in
the anterior
pituitary and bind
to their target cells.
3
Fig. 31.5, p. 509
ANIMATION: Posterior pituitary function
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ANIMATION: Anterior pituitary function
Hormones Secreted by
the Pituitary Gland
Key Concepts
• A Master Integrating Center
• In vertebrates, the hypothalamus and pituitary gland deep
inside the brain are connected structurally and functionally
• Together, they coordinate activities of many other glands
Animation: Hypothalamus and Pituitary
31.5 Sources and Effects
of Other Vertebrate Hormones
• In addition to major endocrine glands, the human body has
hormone-secreting cells in many organs:
• Parts of the gut secrete secretin and other hormones that
affect appetite and digestion
• Adipose (fat) tissue makes leptin, a hormone that acts in
the brain and suppresses appetite
• Kidneys secrete erythropoietin, a hormone that stimulates
maturation and production of red blood cells
• The heart makes atrial natriuretic peptide, that stimulates
the kidneys to excrete water and salt
Sources and Actions
of Vertebrate Hormones
BBC Video: Adrenalin and the Body

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